[1.6.4] Replacing a block in code

[Viral Villager]

Hey people.

 

So I'm trying to make a block to be the top layer of blocks in a dimension I made. I want to make it so when it it pops into existence, it gets placed by a random pre-decided set of blocks. I have the code in place so it decides what block to place, but I'm having major trouble with the actual replacement action. I need to submit my mod soon, so quick help is very appreciated. Please help me out here. Thanks!

 

Viral

 

(PS Here is my current block class: http://pastebin.com/8vGsH9mM )

[Leomelonseeds]

1.6.4 is NO LONGER SUPPPORTED